Vacuum measuring instrument



- NOV. 24, 1931. F SIEBER VACUUM MEASURING INSTRUMENT Filed May 13, 1926Patented Nov. 24, 1931 UNITED STATES PATENT OFFICE BOVEBI 80 C111,LANII? FRITZ SIEBER, OI BA DEN, SWITZERLAND, ASSIGNOR TOAKTIENGESELLSCHAFT BROWN 01' BADEN, SWITZERLAND, A JOINT-STOCK COMPANYOF SWITZER- VAC'UUE MEASURING INSTRUMENT Application filed m 1a, 1926.Serial No. 108,728.

This invention relates to devices for the measurement, indicating anddetection of vacuum. It is of the t pe of such devices known generallyas the ot wire type which depend for their action upon the variation ofdiffusion of heat from a heated wire or the like incident to variationof the density of the surrounding atmosphere. The present invention isdesigned with particular reference to the requirements of metallicvapour rectifiers and similar vacuum apparatus which is employedindustrially.

The general object of the invention is the provision of a device of thetype designated, which is verysimple, compact and strong inconstruction, yet very sensitive, accurate and quickly responsive inoperation.

An important object of the invention is the provision of a device of thesort deslgnated, from which direct readings may be made, the unitarygauge thus functlomng as both a detectin and indicating instrument.

A more speci 0 object is the provision of a device in which temperaturechanges to which it is subjected, other than those resulting from thevacuum changes to be detected, are compensated for m a simple manner.

Another specific object is the provision of a device having thecharacteristics desig-,

nated, which may be employed for the operation of relays, switches orthe like, from which the operation of the vacuum pump may be controlled.

Other and further objects will be pointed out or indicated hereinafter,or will be obvious to one skilled in the art upon consideration of theinvention.

In the drawings forming a part of this specification is shown one formof device embodying the invention, but the claim is not to be construedas limited to this structural form onl y In the drawmgs,

Fig. 1 is a sectional elevation of a gauge taken on a vertical diameter,ancillary portions being shown diagrammatically Fig. 2 is an enlargeddetail showing an edge view of a part of the composite temperatureresponsive coils.

Fig. 3 is a diagram of the o ratin arts of the device shown in Fig. 1, ail d g p Flg. 4 is a similar diagram of a modified form of device whichmay be arranged for operating electric contacts or the like.

Hot wire vacuum tgauges utilize the heatdiilusmg capacity 0 theatmosphere whose density is to be measured as a factor for controllingtheir operation. As the variations of the heat-diffusing capacity of therarified atmosphere, which usually is kept as near vacuum as possible,are quite small, some sort of amplifying indicating device is usuallynecessary to magnify their eliect on the detecting instrument, in orderthat they .5 may be ascertained, either visually or mechanically. Thepresent invention obviates any necessity for such appurtenances as wellas damping arrangements and counterpoises for the indicating element. 70

The nature of the invention ma be ascertained by reference to theexample illustrated. In the drawings, a designates the casing of theinstrument, closed hermetically at the front with a lass panel I), andhaving a connection c wit the vacuum line or container R. In the casingis the calibrated dial (2 visible through the glass. On a bracket 10 ismounted a com osite double spiral 72., formed of a coiled strlp ofmetals having different temperature coeflicients joined after the usualfashion of such elements, as illustrated in Fig. 2, the inner ends ofthe two coils being joined and supportin a spindle g.- The outer ends ofthe coile strips are connected respectively to the terminals 11 leadingthrough the casing. The spindle g carries an arm 7' extending radially,and to the outer end of this arm is connected the outer end of thecompensating temperature responsive coil f, which is a spiral Wound inthe counter-. direction to the spirals h. The inner end of the spiral fcarries a spindle in alignment with the spindle g, and on the same ismounted the pointer e which extends into indicating relationship withthe dial d. 'The terminals i are connected to a source B of continuouselectrical current of constant voltage through a suitable currentequalizing element such as the resistance 1' composed of I.

I iron wire in an atmosphere of hydrogen,

whereby the current is maintained ractically constant. The spindle gleads t rough a partition or shield k interposed between the elements hand ff, to protect the latter from heat radiation rom the former. Theconstructions of the coils h and f are such that they respond in equaldegree to temperature variations.

In the operation of the device, the current from source B heats the coil1)., the resulting expansion ofthelatter varying in accordance with therapidity with which heat is abstractedfrom it by the surroundingatmosphere, the greater the densit of the latter,

' the less will be the amount of eat effective in h to change its form.Expansion or contraca by the compound. strip tion of the actuating coilh willbe effective to rotate the spindle g, the changes of positionbeing indicated by pointer e in relationship to dial d, which may besuitably calibrated to read in degrees of vacuum. Due to the shield is,the compensating coil f is not subject to the heating by the currentfrom source B, as is coil h, but it is subject to the same atmospherictemperature, and as it acts in the counter direction on pointer 6, itfulfills its purpose of compensating the efi'ect of the atmospherictemperature on coil 71., so that the indicating position of pointer ewill represent the determinative heat differential of coil 72..

Owing to the considerable torque developed system, the instrument may befitted wlth limit contacts, as shown on Fig. 4, which operate anelectric alarm or protective circuit when an' upper or lower limit ofvacuum is reached. The moving system comprising the hot spiral k, thecompensating spiral f, and the pointer e is then extended by adding aweak spring m carrying a contact arm n which is efiective to close thecontacts p upon the fixed contacts 0. As long as the arm n does not makecontact the system acts as though the ring m did not exist, but beyondthese limits the weak" torque of the spring m opposes the deflectingtorque of the instrument and thus the graduations on the outer portionsof the scale will be somewhat closer together. If the position of thecontacts o'is definitely fixed,

this correction may of course be incorporated in the scale and nosubsequent correction of the reading will be necessary.

What I claim is In vacuum-measuring apparatus, a casing,

means providing for connection of said cas- I direction andin amountsubstantially directly groportional to temperature conditions in saicasing, and means for maintaining through said last-named meanssubstantially continuous flow of electric current at substantiallyconstant voltage.

In testimony whereof I have hereunto subscribed my name at Zurich,Switzerland, on the 18 day of March, A. D. 1926.

FRITZ SIEBER.

ing with a vacuum line, an indicating element disposed within saidcasing, means operable to lmpart indicating movement to said element 1na glven direction and in amount sub-v stantially directly proportionalto temperature conditions 1n said casing, and means operable to impartindicating movement to said element n the direction opposite to saidgiven'

